This invention relates to an instrument for detecting and measuring the size of particles entrained in liquid chemicals which may have variable viscosities and which may be highly corrosive and more particularly to such an instrument with an improved system for controlling the rate of liquid flow through the particle sensor of the instrument.
In particle measuring instruments for measuring particles entrained in liquids, it is important to maintain a relatively constant rate of flow through the particle sensor of the instrument for different viscosities to achieve accurate and consistent measurement of particle sizes. It is also important to know the amount of the sample that has passed through the particle sensor during a given measurement so that the density of the particles of different sizes can be determined. One method of measuring and controlling the flow rate is to cause the sample to flow into a central chamber of a burette and detecting when the sample overflows the central chamber. The time interval required to fill the central chamber gives a rough measurement of velocity and, by trial and error, the flow rate of the sample can be controlled to be an approximation of the desired rate. The problem with the above described system is that the desired flow rate has to be arrived at by trial and error through several trial runs of filling the central chamber and readjusting the flow rate after each run until the desired flow rate is achieved.
The present invention enables the flow rate to be continuously measured as the sample is passing through the particle sensor enabling the operator to instantaneously control the rate for the given sample. In addition, the system provides an accurate determination of the volume that flows through the sensor so that an accurate measurement of particle density will be obtained.